Fig. 3.

Root-cluster morphologies induced in Proteaceae, Restionaceae, Cyperaceae and Fabaceae by a low supply of phosphorus. All species are well adapted to soils of extremely low P concentrations and endemic to the South West Botanical Province of Western Australia (WA), or the Cape Floristic Region of South Africa (SA). Plants were raised from seed (Proteaceae and Fabaceae) or cuttings (Restionaceae and Cyperaceae) collected from natural habitats, and then grown in nutrient solutions (glasshouses at the University of Western Australia or University of Cape Town) containing ≤ 1 μm [P] (except for the roots of a plant shown in E, which were collected in soil containing ≤ 10 μg P g⁻¹ in Suid Bokkeveld, SA). (A) Proteoid roots (compound type) of Banksia prionotes; acorn banksia (Proteaceae, WA); scale bar = 13 mm. (B) Proteoid root (simple type) of Hakea prostrata; harsh hakea (Proteaceae, WA); scale bar = 4 mm. (C) Dauciform roots of Lepidosperma squamatum (Cyperaceae, WA); scale bar = 2 mm. (D) Dauciform roots of (Tetraria sp. (Cyperaceae, SA); scale bar = 2 mm. (E) Cluster root of Aspalathus linearis; rooibos (Fabaceae, SA); scale bar = 12 mm. (F) Cluster root of the same species shown in E grown in nutrient solution; scale bar = 4 mm. (G) Capillaroid roots of Thamnochortus fracternus (Restionaceae, SA); scale bar = 4 mm. (H) Capillaroid roots of Mastersiella digitata (Restionaceae, SA); scale bar = 6 mm. (I) Capillaroid roots of Chondropetalum tectorum (Restionaceae, SA); scale bar = 5 mm.